The present invention relates to a method and an instrument for manufacturing elements including micro-miniature patterns on a substrate and particularly to an inspecting instrument and a method of inspecting micro-miniature patterns such as the circuits or the like in a semiconductor device and a liquid crystal device and more particularly to an inspecting instrument and a method of inspecting patterns on a wafer that is placed in the course of manufacture of semiconductor device and a method of manufacturing a semiconductor device using the same.
A related art will be explained using an example of inspection of a semiconductor wafer.
A semiconductor device can be manufactured by repeating the process to transfer the patterns formed mainly on a photo-mask to the semiconductor wafer with the lithography and etching steps. In the semiconductor device manufacturing process, since adequacy of lithography step, etching step and the other various steps and generation of particle will give large influence on the manufacturing yield of semiconductor device, the method of inspecting the patterns on the semiconductor wafer in the manufacturing process has been introduced in order to quickly or previously detect generation of irregularity and defect and then feed back such data to the manufacturing process.
As a method of inspecting the defect existing in the patterns formed on a semiconductor wafer, a defect inspecting instrument has been put into the practical use to irradiate a semiconductor wafer with the white light and compare the circuits patterns of the same type of a plurality of LSIs using an optical image. For example, in the inspecting method using an optical image, a method of detecting a defect has been disclosed as described in the JP-A No. H3-167456 in order to focus the light beam to the optical lighting area on the substrate with a time delay integration sensor and then compare such focused image with the previously input design information.
Moreover, the JP-A No. H9-138198 discloses a method of inspecting only particle or defect by detecting the diffracted light beam or scattered light beam through radiation of laser beam and then discriminating the regular diffracted light beam from the circuit pattern and the scattered light beam from particle or defect of irregular shape.
Moreover, with introduction of micro-miniaturization of circuit pattern, complicated shape of circuit pattern and versatile materials, it has now become difficult to detect the defect of optical image. Therefore, there is proposed an inspection method through comparison of circuit patterns using an electron beam image having the higher resolution that of the optical image.
As the pattern comparison inspection instrument using electron beam, Journal of Vacuum Science and Technology B, Vol. 9, No. 6., pp. 3005-3009 (1991), Journal of Vacuum Science and Technology B, Vol. 10, No. 6, pp. 2804-2808 (1992), JP-A No. H5-258703, U.S. Pat. No. 5,502,306 and JP-A No. H10-234543 disclose a method to automatically detect a defect by irradiating a conductive substrate (X-ray mask or the like) with the electron beam having an electron beam current that is 1000 times or more (10 nA or more) the ordinary SEM, detecting any one of generated secondary electron, reflected electron and transmitting electron and then comparing the image formed from such signal for the inspection purpose. This inspecting method is called hereinafter the wafer inspection system using electron beam.
In the wafer inspection using electron beam, an image having the resolution higher than that of the wafer inspection system or the inspection using laser can be obtained. Therefore, an ultra-miniature particle or defect on a micro-miniature circuit pattern can be detected. In addition, conductivity/non-conductivity of circuit pattern, electrical defect such as wiring and short-circuit of transistor generated at the surface or lower layer can be detected from voltage contrast reflecting potential difference at the surface on the secondary electron radiation efficiency due to the influence of charging by radiation of electron beam. The voltage contrast and the technology using the same are disclosed on the pages 839 to 841 of the xe2x80x9cELECTRON, ION BEAM HANDBOOKxe2x80x9d (Published by Nikkan Kogyo Shimbun Co. Ltd.).
In the wafer inspection system and inspection using the laser, particle and defect of circuit pattern shape are detected. For the particle and defect detected, it is required to observe in detail the contents thereof in order to identify the cause of generation. Therefore, a method is now employed to receive the positional information of particle or defect detected with each inspection instrument through a communication network or medium and observe such information in the high magnification factor and high resolution with an optical microscope unit image, laser microscope unit image or electron beam image. With development in micro-miniaturization of pattern and defect or particle detected, an electron beam image can be observed in detail with the higher resolution in comparison with the optical microscope unit image or laser microscope unit image. Therefore, the observation method by the electron beam image is now widely employed. The observation instrument using such electron beam image is called, hereinafter, the review SEM.
The review SEM and an observing method in this review SEM are respectively disclosed in the JP-A No. H9-184715 and No. H10-135288. In regard to the particle and pattern defect detected with the wafer inspection system and laser inspection system as explained above, detail shape observation has become possible using the review SEM that can allocate the observation area and observe this area with the electron beam image by receiving the positional information of these inspection instruments.
However, in the wafer inspection system using electron beam, an electrical defect such as short-circuit or disconnection of transistors generated in the lower layer even if there is no irregular phenomenon in the shape of surface can be detected through the voltage contrast. It has been attempted to observe the detail of such electrical defect detected with such wafer inspection system using electron beam with an ordinary SEM, wafer inspection system or review SEM but it has been accompanied with the problem that voltage contrast cannot be obtained, disabling the observation. Regarding this problem, the review SEM that enables both high resolution observation of particle and pattern shape defect and detail observation of electrical defect that can be realized with voltage contrast has not yet been proposed in the related art.
As is explained above regarding the related art, as a result of application of wafer inspection system using laser in addition to wafer inspection system and inspection system using laser to various ultra-fine circuit patterns as well as semiconductor device, it has become possible now to detect the defects such as particle and pattern figure defect and various defects such as electrical defects like the open/short-circuit of transistors and the defects such as conductivity defect of hole pattern or the like that cannot be detected only from the figure of surface.
In order to improve the circuit pattern manufacturing process based on the result of defect detection with the wafer inspection system using electron beam, it is necessary to review in detail the contents of detected defect and execute the detail classification of particle, defect in the figure and electrical defect or the like to identify the cause of generated defect from the review result and classification result.
On the occasion of reviewing irregularity and particle in the figure of surface using the review SEM, it is effective to introduce a method of reviewing the SEM image that can be obtained by irradiating the review area under the high resolution condition that is realized with the electron beam squeezed to narrow beam and then detecting the generated secondary electron beam. In the case of SEM image, since the surface roughness information is included in the reflected electron generated when the review object is irradiated with the electron beam, it is effective to introduce a method to detect and review the reflected electron including the surface roughness information on the occasion of reviewing the surface height condition of the review object. Therefore, in order to simultaneously review the figure and material information and surface roughness information, it is preferable to install a plurality of detectors to discriminate and detect the figure and material information and the surface roughness information. On the other hand, the observation conditions such as electron beam current and scan speed or the like that are suitable for review of electrical defects from the voltage contrast are different from the conditions that are suitable for review of surface figure defect and particle.
In the cited references, the review SEM for reviewing in high resolution the surface and particle figures has been described, but these also include a problem that the observation conditions that are suitable for observation of electrical defects cannot be set easily. Thereby, this review SEM has always been accompanied with the problem that the electro-optical conditions must be manually set depending on the review purpose and therefore adjustment requires a large amount of time and labor.
Moreover, in the review SEM, it is required to receive the positional information of the defect detected with various kinds of inspection instruments with communication or medium and an image of defect is formed by scanning to the defective position and therefore high accuracy positioning is necessary to review fine particle and defect. In the method and instrument of the related art, rotation has been compensated through the alignment using the patterns of two points on the wafer as the review object, but such compensation has a problem in reception of positional information pieces among various instruments that a delicate deviation is generated in the magnification factor of coordinate system and in the positional information and thereby the position is displaced at the time of extracting the sight of defective position.
Moreover, in various inspection instruments, various inspections are executed for the wafers that are manufactured from time to time in the semiconductor manufacturing process. Therefore, a large amount of particles and defects can be detected. It is of course required to know the detail contents of the detected defect and particles, but in this case, a problem rises that a large amount of time is required in such a case that all defects of all wafers are reviewed with the existing review SEM. Therefore, it has been requested to select the review areas from a large amount of defects for the highly efficient detection of characteristics of defects. Moreover, it has also been required to review and classify the selected defects automatically at a higher speed.
It is a first object of the present invention to provide a pattern inspecting instrument and a method of inspecting pattern for inspecting a fine pattern such as a circuit on the substrate surface of semiconductor device or the like by radiating thereto a white beam, laser beam or electron beam in order to efficiently inspect, review and discriminate, within a short period, various particles and defects such as the detected surface roughness, defect of figures and particles and moreover electrical defects.
Moreover, it is a second object of the present invention to provide a pattern inspecting instrument and a method of inspecting pattern for realizing high-speed and highly accurate review and classification of various particles and defects explained above.
Moreover, it is a third object of the present invention to provide an inspection instrument and an inspection method that assure, through application to various kinds of semiconductor devices in multiple steps and the other fine circuit patterns in the earlier stage, highly efficient detection of process defect of semiconductor device or the like, reflection of the result on the manufacturing conditions, enhancement of reliability of semiconductor device and reduction of failure rate.
Particles and figure defects on circuit patterns and defects such as electrical open/short-circuits can be detected automatically by executing various inspections of the type for comparing the images obtained through radiation of white beam, laser beam and electron beam with the adjacent similar patterns in the substrate of semiconductor device including fine circuit patterns. However, such inspection instrument provides the positional information generated by a defect and the size of defect. In order to obtain detail contents of defect, it is required to acquire again a high resolution image at the defect generating area and classify the contents of defect from the image information in regard to the figure, roughness and material and others.
In the related art, even in the length measuring SEM and review SEM, a beam current radiated to a sample has been reduced, a plurality of images of the same area have been obtained and added to form an image in order to review the fine figure in higher resolution. In such an image forming method, a fine figure can be reviewed but it has been difficult to review electrical defects through the voltage contrast. In other words, when the open or short defect detected with the wafer inspection system using electron beam is reviewed with the review SEM, the defect often cannot be recognized.
The inventors of the present invention have found that the review area must be charged to review an electrical defect using the voltage contrast and a large beam current to be radiated is preferable for better charging. However, since it is also required to obtain the voltage contrast and execute the detail surface review in the same review process, a beam current that can maintain high resolution must be selected. Moreover, the same inventors have found that various electrical defects can be reviewed with the same instrument by adequately changing the beam scan speed depending on contents of electrical defects.
The inspection instrument of related art has a problem that a large amount of steps such as beam axis adjustment and luminance adjustment is required to change the optical conditions for radiation of electron beam and detecting conditions thereof because various parameters of instrument are fixed only to review the fine figure. However, as is already explained, electrical defect must also be reviewed together with fine figures with the same instrument and therefore simple setting must be assured for the electron beam radiating condition for reviewing of figures, conditions for reviewing figures and conditions for reviewing electrical defects.
The inventors of the present invention have also found that different electron beam radiating conditions, lens conditions and signal detecting conditions can be set easily by storing and registering the files of the conditions suitable for fine figure review as the xe2x80x9cfigure review modexe2x80x9d, the conditions suitable for review of roughness as the xe2x80x9croughness review modexe2x80x9d and the conditions suitable for review of electrical defect as the xe2x80x9cvoltage contrast review modexe2x80x9d.
Moreover, as the electron beam radiating conditions, small beam current is preferable for high resolution review in the xe2x80x9cfigure review modexe2x80x9d. On the other hand, in the xe2x80x9cvoltage contrast review modexe2x80x9d, a large radiation beam current is preferable for more effective charging of the sample surface since review is conducted using the phenomenon that brightness of SEM image is different in the normal circuit pattern and defect generating pattern because amount of secondary electrons reaching the detector changes depending on electrical characteristic when the surface is charged and energy of secondary electrons generated from the surface of sample also changes. Moreover, the charging condition of the sample surface can be controlled and defective area can also be visualized from the SEM image by changing the electron beam scan speed depending on contents of electrical defect. In the xe2x80x9croughness review modexe2x80x9d, it is not particularly required to control the beam radiating conditions because this mode is not easily influenced by the radiated beam current and scan speed.
Next, the same inventors have also found the following conditions to detect the signal that is generated simultaneously generated from the sample surface when the sample surface is radiated with the electron beam. In the xe2x80x9cfigure review modexe2x80x9d, the secondary electrons generated from the surface of sample are detected and in the xe2x80x9croughness review modexe2x80x9d, the reflected electrons are detected. In the xe2x80x9cvoltage contrast review modexe2x80x9d, only the secondary electron of the predetermined energy among the secondary electrons is detected in order to obtain respective information pieces. Therefore, it has also been found that the information pieces of xe2x80x9cfigurexe2x80x9d, xe2x80x9croughnessxe2x80x9d and xe2x80x9cvoltage contrastxe2x80x9d can be individually visualized and detected by detecting as explained above the secondary electron and reflected electron generated from the surface of sample when the surface is radiated with the electron beam.
Moreover, it has also been found that the xe2x80x9croughnessxe2x80x9d can also be reviewed simultaneously by detecting the reflected electron simultaneously with the figure through detection of the secondary electron in the xe2x80x9cfigure review modexe2x80x9d. In the same manner, the xe2x80x9croughnessxe2x80x9d can also be reviewed simultaneously by detecting the reflected electron at the time of detecting the secondary electron having higher energy in the xe2x80x9cvoltage contrast review modexe2x80x9d.
Next, it has also been found that the adequate review conditions can be set on the occasion of reviewing the defect by setting the xe2x80x9cfigure review modexe2x80x9d in the wafer inspection and defect inspection after inspection using laser because electrical defect cannot be detected in the wafer inspection and inspection using laser and on the other hand, the adequate review conditions can be set automatically at the time of reviewing the defect by setting the xe2x80x9cvoltage contrast review modexe2x80x9d in the defect inspection after execution of the wafer inspection to detect electrical defect.
In addition, it is also found that the target defect can be reviewed easily when the electron beam radiating conditions and signal detecting conditions can be set depending on the selection by providing an input image for selecting the xe2x80x9cfigure review modexe2x80x9d and xe2x80x9cvoltage contrast review modexe2x80x9d in the interface image and then selecting the review mode from this input image. Moreover, in regard to the xe2x80x9croughness review modexe2x80x9d, the xe2x80x9croughnessxe2x80x9d can be reviewed freely even in the xe2x80x9cfigure review modexe2x80x9d and xe2x80x9cvoltage contrast review modexe2x80x9d by selecting the xe2x80x9croughness review modexe2x80x9d.
The review for fine figure and roughness information and review for electrical defect can be realized freely depending on the purpose by executing these inspection methods and using the inspection instrument including these functions. A means for realizing the inspection method in the present invention will then be explained hereunder.
According to the present invention, as the first means, the electron beam radiating and signal detecting conditions that is suitable for voltage contrast review can be set. As the condition suitable for voltage contrast, a beam current is set to a comparatively higher level, radiation energy is set to a comparatively higher level and scan speed is set to comparatively higher rate for the open defect but to lower rate for the short defect. Moreover, in regard to the detection system, an energy filter is used to provide a function to detect only the signal having the energy larger than the predetermined energy applied to the energy filter in view of discriminating a difference between amounts of secondary electrons in different energy distributions generated from the normal area and defective area due to the influence of surface potential. Thereby, electrical defect can be recognized with the voltage contrast in comparison with the existing method to review, without use of the energy filter, in the same condition that a beam current is small.
As the second means, any review condition can be set easily almost without any adjustment by registering, as the table or file, various electron beam radiating conditions and signal detecting conditions that are suitable for recognition of electrical defect explained in above first means as the xe2x80x9cvoltage contrast review modexe2x80x9d, then registering various electron beam radiating conditions and signal detecting conditions that are suitable for fine figure review as the xe2x80x9cfigure review modexe2x80x9d and moreover registering the signal detecting condition that is suitable for review of surface roughness and height as the xe2x80x9croughness review modexe2x80x9d.
As the third means, various filtered energy signals are individually detected by providing an energy filter in the signal detecting system and allocating a plurality of detectors under the electron beam radiating condition that is suitable for review of voltage contrast described for the first means explained above. Thereby, the xe2x80x9cvoltage contrast modexe2x80x9d, xe2x80x9cfigure review modexe2x80x9d and xe2x80x9croughness review modexe2x80x9d can be set by changing only the detecting condition in the same electron beam radiating condition by reviewing the figure information with the detecting signal mainly formed of secondary electron, the surface roughness information with the detecting signal mainly formed of reflected electron and voltage contrast with the detecting signal mainly formed of secondary electron having higher energy level. Namely, adjustment of optical axis is no longer required.
As the fourth means, highly accurate positioning can be realized even in the case of extracting a sight of defect at the area separated from a die to which alignment is performed by obtaining images of the circuit pattern for alignment in the first die and the circuit pattern for alignment in the second die and then also obtaining not only the compensated information of positional deflection and rotation but also the error of magnification factor of the coordinate system at the time of executing the alignment of positional information of two dies.
As the fifth means, more highly accurate compensation for position can be realized by further reviewing the predetermined particles and defects after the alignment of position and rotation using the predetermined pattern and then further compensating for he position information from the position of particle/defect within the sight.
As the sixth means, the above xe2x80x9cvoltage contrast review modexe2x80x9d and xe2x80x9cfigure review modexe2x80x9d or the like can be set automatically by reviewing, with the review SEM, the detection result information including coordinate data of defect and the code of inspection instrument when the inspection is executed with an inspection instrument and the result is output to the external circuit. Namely, conditions for automatically executing the review can be set easily by automatically selecting the figure review modexe2x80x9d when the defect data obtained by inspection with a wafer inspection instrument and an inspection instrument using laser beam that cannot detect an electrical defect and also setting the xe2x80x9cvoltage contrast review modexe2x80x9d depending on the inspection conditions when the defect data obtained by the wafer inspection system using electron beam that can detect electrical defect is read.
As the seventh means, automatic setting of review can be realized easily by allocating, within the image, an input unit for selecting the review condition such as xe2x80x9cvoltage contrast modexe2x80x9d, xe2x80x9cfigure review modexe2x80x9d and xe2x80x9croughness review modexe2x80x9d and also allocating an input unit for selecting the review area at the image for setting the review condition with review SEM.
As the eighth means, a means is provided for switching the review sequence from the nearer defect in the process to automatically execute the review/image review/classification of defect contents for a plurality of defective areas with the review SEM.
As the ninth means, review conditions can be set easily through the process that the detail instrument conditions are not displayed in direct in the main menu as the sub-menu by providing, in the display image for setting the review conditions, the main menu display image to select the inspection conditions in order to set the review conditions with the simplified menu selection.
Thereby, the important parameter input for review can be realized only with the interface operations for selecting the menu without the complicated input operations.
With the means explained above, not only the surface figure review of the prior art but also the review of electrical defect can be realized in the inspection of the substrate having a fine circuit pattern as well as the semiconductor device to review the details of detected defect. Moreover, the adequate review conditions can be set easily without any adjustment of optical axis as required by previously registering the review condition suitable for figure review and the condition suitable for electrical defect review as the instrument condition for enabling the selection in the setting condition file to determine the inspection condition. Moreover, the highly accurate sight detection of defect can be realized by executing magnification factor compensation by two points in the alignment and the positional information compensation by actual defect and particle. In addition, review conditions can be set easily by displaying, in the interface display image of inspection instrument, the condition file having an input unit for determining the review mode and review area.
The electrical defect that has been difficult for review with the prior art can be reviewed easily, moreover review condition setting and instrument adjustment that have required a longer time in the review of electrical defect can be realized only with the simplified operation such as selection of review condition file and moreover the review parameter setting that have required a longer time in generation of the review condition file can be realized efficiently within a short period of time by reviewing a substrate having a circuit pattern, for example, a semiconductor device using the review method and review system explained above after the review thereof with an inspection system. As a result, the detail contents of the figure defect of pattern, fine particles, electrical continuity defect and short-circuit generated in the process of the steps for manufacturing a semiconductor device can be detected quickly and problems included in the process or manufacturing system condition can then be visualized. Therefore, the cause of defect in the manufacturing process of each substrate as well as the semiconductor device can be searched in the higher speed with higher accuracy than that in the existing method and instrument. As a result, higher manufacturing yield, namely lower failure rate can also be assured and simultaneously TAT until an adequate measure is taken from detection of defect can also be reduced.